Take a slip with the Spit14 and fixed. I know there is a push to unperk the 14, but I say leave it as a cheap perk ride. A deck speed of 345-ish is avg for the MA. The 14 can do 361 on the deck iirc. That edges the likes of the G14,Yak9U and F4U1A.
P-47N: Excellent ord, roll. Good speed but poorest performance without WEP of ANY jug. This seems like a good candidate for raising ENY but showed up late in war. Leave at 10ENY.
P-47M: Better K/D than Pony. Better gun package, better climb with WEP, better angles fighter, much better toughness. No A-G capability but it was a rarity in RL (130 built) and this should be reflected a little. (5 ENY)
F6F: Compared to 20 ENY P47D40 the Hellcat has worse: A-G ord, flaps, roll, guns, visibility, toughness, dive, and SPEED. The F6F has a climb (maybe, and only below 10k), a tailhook and turn going for it. The Hellcat's rearward visibility is probably the worst of any fighter off the top of my head. The F6F was a major US type and sees the least use of any US of LW ride. Even with an ENY increase, I don't see the F6F reaching parity with the F4U-1D to say nothing of the F4U family as a whole. (20 ENY)
Ki84: One of the best K/D in game and it is at 20 ENY. I'd compare it to a fast Spit9 (which is 20 ENY btw) with A-G capability and much better fuel economy. (15 ENY)
Seafire: This 15ENY ride has vastly inferior performance to Spit9 with exception of turn. It is as the F6F is to the D40. (20 ENY)
Brew: Leave as is. It is not a threat to most birds. A6M5b has better speed and climb. (25 ENY)
109K4: This is a monster. Arguably the best all-round E fighter in the game. The Spit 14/16 can give it problems but it is tougher and faster. Faster than a Pony at some alts, decent turn, outstanding climb. Would be even lower if the tater weren't so difficult to use. (15 ENY)
A20: 10 ENY.
110G-2: 15 ENY. Sure the firepower is awesome but it is at a handicap in MA A-A engagements. In the same boat as the 47N imho.
190D9: Sure it can't flat turn a Pony but it outruns a Pony, has far more WEP, cannons w plenty of ammo, better climb/accel, and rolls like crazy. It might even be a tad tougher than the Pony too. Lack of turn and ord keep it a notch below the Pony. (10 ENY)
8 Changes in total...pretty few gripes when you take the size of the planeset into account right?